1. Field of the Invention
The present invention relates to a sheet processing device that binds paper sheets carried out from an image forming device such as a copier or a printer and folds the bound paper sheets at a predetermined folding position and, more particularly, to a sheet processing device capable of performing binding processing suitable for intended use when binding a paper sheet bundle at a portion around a center thereof and then folding the bound paper sheet bundle.
2. Description of the Related Art
There are widely known processing devices that fold a paper sheets carried out from an image forming device in a booklet form. These processing devices are provided with a sheet stacking means for sheet processing. In the sheet stacking means, the paper sheets are stacked in a bundle and are then saddle stitched and folded in a booklet form. Further, in recent years, a binding device that binds a paper sheet bundle without use of a metallic binding needle (metallic staple) in the sheet bundle binding processing and a processing device using such a binding device are being provided.
For example, Jpn. Pat. Appln. Laid-Open Publication No. 2011-201698 discloses a device that performs bookbinding without use of a metallic binding staple so as to enhance recyclability and safety of the bound recording material bundle. In this device, a folding blade and a folding roller apply folding to a paper sheet bundle stacked on a stacker for stacking a plurality of paper sheets in order. A binding mechanism section binds the paper sheet bundle, without use of the metallic staple, in a position at a predetermined interval from a folding position where the paper sheet bundle is subjected to folding by the folding blade and the folding roller.
In the binding processing, the binding mechanism section causes deformation in a thickness direction of the paper sheet bundle that has been subjected to folding by the folding blade and the folding roller so as to bind the paper sheet bundle. More specifically, upper and lower concavo-convex teeth crimping teeth are meshed with each other to cause local deformation in the thickness direction of the paper sheet bundle to make the paper sheets to be engaged with each other.
Besides, there is known a cutter mechanism as a different type of binding mechanism from the binding mechanism using the crimping teeth. The cutter mechanism makes a cut in the paper sheet bundle for deformation of the cut part so as to bind the paper sheet bundle. More specifically, the cutter mechanism binds the paper sheet bundle by means of a U-shaped blade for making a U-shaped cut in the paper sheet bundle, a slit blade for forming a slit-like cut of a length corresponding to a width of the U-shaped blade, and a pushing-in means for pushing the U-shaped cut formed by the U-shaped blade in the slit-like cut.
In either of the above two mechanisms, a portion to which the binding mechanism applies binding is set so as to be separated by a predetermined interval from the folding position of the paper sheet bundle (refer to FIGS. 7 and 11 of Jpn. Pat. Appln. Laid-Open Publication No. 2011-201698). In other words, the folding position and binding position are shifted from each other.
International Publication No. WO2010-067587 discloses a bookbinding system in which an adhesive applying device and a binding device using a metallic staple are connected to each other. Particularly, as illustrated in FIGS. 13, 20, and 24, this system includes a unit provided with the adhesive applying device that applies an adhesive to conveyed paper sheets and a binding/folding unit provided with a needle binding mechanism that applies needle binding processing to the paper sheets and a folding mechanism that folds in half the bound paper sheets are connected in a horizontal direction.
Jpn. Pat. Appln. Laid-Open Publication No. 2011-190021 discloses a sheet processing device having, in a tray, a stapler and a stapleless binder which are configured to bind a paper sheet bundle at its corner portion, in which the stapleless binder is disposed at a position closer to an eject roller for discharging the paper sheet than the stapler.
Jpn. Pat. Appln. Laid-Open Publication No. 2012-45879 discloses a bookbinding device that punches a punch hole while changing hole positions for each paper sheet or a plurality of paper sheets for ring binding. The position of the punch hole is calculated based on the number paper sheets and thickness information.
Japanese Patent No. 4,952,129 discloses a stapler device that uses a paper-made staple in place of a metallic staple in consideration of environment and safety. In this device, an operator manually inserts a paper sheet bundle into a binding processing port. More specifically, Japanese Patent No. 4,952,129 discloses a desk-top type stapler device. In this device, a paper-made staple at the top of a connected staple in which a plurality of paper-made staples are connected in parallel is cut off from the connected staple and shaped into a substantially U-form. Then, both leg portions of the paper-made staple are made to penetrate paper sheets to be bound, bent along the paper sheets to be bound, and then bonded to each other. With this configuration, it is possible to bind the paper sheets to be bound with an easily deformable paper-made staple.
The above-described binding device disclosed in Jpn. Pat. Appln. Laid-Open Publication No. 2011-201698 performs binding processing by deforming the paper sheet bundle itself or by forming a cut bent in a convex shape on one side of a paper sheet bundle and then inserting paper sheets into the formed cut. However, in this configuration, a metallic staple cannot be used for saddle stitching of the paper sheets.
In general, the binding processing not using the metallic staple takes much time for the binding. Thus, in order to realize different binding methods, i.e., a binding method using the metallic staple for raid processing and a binding method not using the metallic staple but using deformation of the paper sheet or cut formed therein for environmental protection, it is necessary to use different devices. That is, it is impossible for one device to realize both the binding method using the metallic staple and that not using the metallic staple.
Further, in the stapleless binding for the saddle stitching disclosed in the above publication, the folding position and binding position are shifted from each other, a saddle stitched booklet cannot be opened at the folding center, thus restricting a print range and causing a feeling of strangeness.
The above International Publication No. WO2010-067587 discloses the bookbinding system in which the adhesive applying device and binding device using the metallic staple are connected to each other. The adhesive applying device and binding device using the metallic staple are configured as separated units, thus increasing an installation area. Thus, a sheet conveying distance from the adhesive applying device not using the metallic staple to a folding device is increased, so that when the binding is performed only by application of the adhesive, peeling or turning-up of the bonded portion may occur on the sheet conveying path.
The above Jpn. Pat. Appln. Laid-Open Publication No. 2011-190021 discloses the stapler that uses a metallic staple to be driven at a corner portion of the paper sheet and stapleless binder that binds the paper sheets, without the metallic staple, by pressing/deforming the paper sheets, but does not mention a positional relationship between the stapler and stapleless binder when the paper sheets are saddle stitched.
The above Jpn. Pat. Appln. Laid-Open Publication No. 2012-45879 discloses a bookbinding device that provides a dedicated ring bind for an end face of the paper sheet bundle to perform ring bookbinding but is not a device that performs processing close to simple ring bookbinding for the paper sheet bundle to be folded.
The above Japanese Patent No. 4,952,129 discloses the manual stapler device that uses a paper-made staple, but does not mention at all automation of the folding device or saddle stitching of the paper sheets.
Under such a situation, a main object of the present invention is to provide a sheet processing device that performs saddle stitching processing that binds a bundle of stacked paper sheets at a position around a center thereof and then folds in half the paper sheet bundle at the binding portion, the device being capable of selectively performing both saddle stitching not using a metallic staple but using a method other than binding using the metallic staple and high-speed saddle stitching by using the metallic staple in accordance with intended use, and capable of reducing a size, and an image forming device provided with the sheet processing device.